The positive thing is that it mobilizing at the office can constitute a nice break from just sitting inefficiently at your desk - and it is easy and quick.
My recommendation is that you spend (at least) 5 minutes a month, focusing on your hips and shoulders. Remember to start slowly and aim low, just try to be a little better than yesterday or last month:
1. Squat. Sit as low as you can in a normal squat position for 1-2 minutes, straight back with no "butt dipping", feet about shoulder width, slightly pointed outward. For extra credit, vary the feet position from very narrow to very wide.
2. Shoulders. Lie on your back, put your feet to tha floor and push the hip and back up in the air. Position your forearms under your back. Make sure your shoulders are firmly in contact with the floor, then lower your hip, thus pressing your forearms toward the floor. Move your hip up and down in very slow movements straining your shoulders more respectively less. Constantly strive to keep your shoulders in contact with the floor throughout the exercise.
3. Hips. Do the "couch stretch" at least one minute on each side. Se picture of me (hungover in Visby this summer) to the right, as well as at the office:
Couch stretch in Visby
Saed is showing what a butt dip looks like. Avoid that.
Couch stretch at the office
And if you have a foam roller you should think about mobilizing your torso by lying on it and trying to bend your back over it (without letting your lower part of the back do the bending)
When you think you are ready for more, gradually add the following exercises for a couple of minutes each. Sooner or later you'll be mobilizing 5 minutes per week (!) if you feel like it:
Calves, achilles tendon. Either with the foot blade up against a wall, or by sitting in a narrow squat, balance as far forward as possible and shift your weight to one foot at a time
Hamstrings. Lie on your back, grab one foot at a time with the leg bent. Straighten the leg and pull it closer to your head. Try straining against your pull for five seconds and then relax and take the opportunity to go deeper inte the stretch (straighter leg and closer to the head) during the relaxation
Also try these:
Bully grip (with head turn, and lowering of body for increased tension and leverage). TBG needs a minimum of equipment; something to grab a hold on with your arm behind your back
Glutes (do them in your office chair or in the TV sofa)
Shoulders. Just hang out for a while like this. Grab something overhead, turn your palm facing from you. It improves your overhead press position.
If you are still looking for more, try some self massage techniques:
1. Shoulders. Place a tennis ball, lacrosse ball or similar object under your scapula while lying on your back. Move around and explore the edge of the entire scapula with the ball, including your traps (trapezius). Try doing air bench presses in that position, or air overhead presses, and back strokes
2. Shoulders. Lie face down with a ball under your shoulder or pecs (pectorals). Explore.
3. Glutes/Hamstrings. Sit on a ball. Do leg extensions while sitting on the ball
4. Psoas. Lie face down with the ball a few inches to the side of the navel (umbilicus). Attack your psoas from the side, with the ball, utilizing your body weight. Do the same with the ball right below your hip bone instead
5. Legs and forearms. Press and roll the ball on your calves, your forearems and thighs. Put extra pressure on the tear drop part of the quads by using your body weight (face down, bent leg)
6. Feet. Place the ball under your foot arch, put weight on it and roll back and forward with focus on the inside of the foot; the arch
7. Lats. Don't forget your lats (latissimus). Lie on your side on a ball or a foam/tube roller and more or less aim for wherever it hurts the most.
If you are really serious about extreme stretching and mobilizing you should check out Kelly Starret's MWODs etc., starting here.
But remember, the first 3-4 exercises at the top of this post are what makes the biggest change to anybody who sits a lot and haven't thought about doing mobility exercises. Aim for 5 minutes a month to begin with. That should make a world of difference for you.
This stuff is only for competetive athletes or show-offs and is hardly beneficial to your health:
A "few" years back
When I still practiced martial arts
This one is border-line. It's probably good but this might just be over the top:
I always end up in that position when relaxing between other stretches